Gas barrier changes and structural alterations induced by retorting in a high barrier aliphatic polyketone terpolymer

Abstract

Analysis of the consequences of a typical humid thermal plastic food packaging sterilization (retorting) process over the crystalline morphology and gas barrier properties of a high barrier aliphatic polyketone terpolymer was carried out by in situ simultaneous synchrotron WAXS and SAXS experiments an by DSC, ATR-FTIR spectroscopy, and oxygen transmission rate measurements. From a structural view point, it was observed that the retorting process led to a less crystalline material; however, crystallinity was fully restored by a postdrying process. The humid thermal treatment also favored the sorption of moisture in the amorphous phase to a saturation level, i.e., 2% water uptake. As a result, the oxygen permeability at 21°C was observed to increase by about nine times immediately after the humid treatment, but the barrier character was observed to quickly recover over time. From the results, it is suggested that a simple postdrying process at moderate temperatures can restore morphology and barrier properties. In the overall, it is also suggested that aliphatic polyketones withstand far better the process of retorting in comparison with, for instance, other high barrier polymers such as ethylene-vinyl alcohol copolymers reported earlier and can therefore offer even as a monolayer an alternative in retortable food-packaging applications.

The Role and Potential of Vibrational Spectroscopy in the Study and Characterization of Traditional and Novel Food Packaging Structures

“…11 The effects of retorting on the molecular structure of other food packaging materials have also been studied using attenuated total reflection (ATR) FT-IR spectroscopy. While retorting did not substantially alter the molecular organization of aliphatic polyketones, 12 the humid heat treatment led to crystal development in amorphous polyamides (aPAs) as inferred by the changes in shape, position, and relative intensity of several absorption bands. 13 It is known that when a polymer sample crystallizes, new absorption bands and/or narrowing of the spectral features is often observed because of an increase in conformational regularity and other effects like factor group splitting, etc., that result from crystallization.…”

Progress in polyketone materials: blends and composites

“…Even if POK is exposed to high temperature for a long time, the gas transport properties are not substantially affected . Therefore, POK holds great potential to be applied in vacuum‐insulating or packaging such as liquid hydrocarbon containers or even as an alternative in retortable food or medical packaging …”

“…After humid treatment, a decrease in oxygen barrier properties was observed, but the barrier properties can recover over time quickly. This was most likely caused by water vapor ingress and subsequent decrease in the intermolecular and intramolecular cohesion of the amorphous phase and water desorption and the subsequent increase in molecular cohesion or self‐association leading to barrier improvement over time …”

“…6 Therefore, POK holds great potential to be applied in vacuum-insulating 6,86 or packaging 5 such as liquid hydrocarbon containers 88 or even as an alternative in retortable food or medical packaging. 89 Nobile et al 6,86 investigated the permeabilities of POK at several temperatures (from 25 to about 65 ∘ C) with five different gases (oxygen, nitrogen, methane, ethane and carbon dioxide). It was found that POK showed good barrier properties under all those conditions although the test temperatures were above the glass transition temperature of POK.…”

The role of a polyester-based thermoplastic elastomer in the crystallization of an aliphatic polyketone terpolymer

“…Favorable properties such as high tensile strength, high wear resistance, low gas permeability and high chemical resistance give EPCO great potential as an engineering plastic and a barrier packaging material. [1][2][3][4][5][6][7][8][9] However, control of the temperature to below 240°C is recommended for the melt fabrication process of EPCO because thermal degradation occurs readily at a higher temperature. [10][11][12][13][14] This is a result of residual palladium, the polymerization catalyst, for EPCO, which frequently causes trouble in the melt processing of EPCO because of a very narrow processing window.…”